{
    let str='abc'
    console.log(str.indexOf('o'));
    console.log(str.indexOf('b'));
    console.log(str.includes('o'));
    console.log(str.includes('b'));
}
{
    let str='Hello world!'
    console.log(str.startsWith('H'));
    console.log(str.startsWith('e'));
    console.log(str.startsWith('world',6));
}
{
    let str='Hello world!'
    console.log(str.endsWith('world',5));
}
{
    let str='ab';
    console.log(str.repeat(2));
}
{
    console.log("5".padStart(2,"0"));
    console.log("5".padEnd(2,"0"));
    
}